Michigan Technological University Digital Commons @ Michigan Tech
Dissertations, Master's Theses and Master's Reports
2016
COMPETITION VEHICLE BASED INTAKE MANIFOLD DESIGN
Joshua N. Matiash Michigan Technological University, [email protected]
Copyright 2016 Joshua N. Matiash
Recommended Citation Matiash, Joshua N., "COMPETITION VEHICLE BASED INTAKE MANIFOLD DESIGN", Open Access Master's Report, Michigan Technological University, 2016. https://doi.org/10.37099/mtu.dc.etdr/281
Follow this and additional works at: https://digitalcommons.mtu.edu/etdr Part of the Automotive Engineering Commons, and the Heat Transfer, Combustion Commons
COMPETITION VEHICLE BASED INTAKE MANIFOLD DESIGN
By
Joshua N. Matiash
A REPORT
Submitted in partial fulfillment of the requirements for the degree of
MASTER OF SCIENCE
In Mechanical Engineering
MICHIGAN TECHNOLOGICAL UNIVERSITY
2016
© 2016 Joshua N. Matiash
This report has been approved in partial fulfillment of the requirements for the Degree of MASTER OF SCIENCE in Mechanical Engineering.
Department of Mechanical Engineering – Engineering Mechanics
Report Advisor: Dr. Scott A. Miers
Committee Member: Dr. James DeClerck
Committee Member: Dr. David D. Wanless
Department Chair: Dr. William W. Predebon
Contents
Abstract ...... 5
1 Introduction ...... 6
1.1 Background ...... 6
1.1.1 FSAE Competition ...... 6
1.1.2 Intake Manifold Tuning ...... 7
1.2 Hypothesis ...... 8
2 Procedure ...... 9
2.1 On-Track Torque Usage Investigation ...... 9
2.2 Engine Model Development ...... 11
2.2.1 Engine Dynamometer Testing ...... 11
2.2.1.1 Engine Instrumentation ...... 11
2.2.1.2 Dynamometer Setup/Testing ...... 15
2.2.2 GT-Power Model ...... 16
2.3 Intake Design ...... 18
2.3.1 Intake Geometry Design of Experiments ...... 18
2.3.2 CAD Model Development ...... 19
2.4 Final Validation ...... 19
3 Results and Discussion ...... 21
3.1 On-Track Torque Usage Findings ...... 21
3.2 Dynamometer Testing Results ...... 25
3.3 GT-Power Model Calibration ...... 26
3.3.1 Model Air and Fuel Flow Calibration ...... 26
3.3.2 Combustion Model Calibration ...... 27
Page 3 of 57 3.3.3 Torque Calibration ...... 30
3.4 Intake Geometry Refinement Results ...... 31
3.5 CAD Model Development and 3-D Printing ...... 32
3.6 Performance Comparison ...... 35
3.6.1 Dynamometer Performance Comparison ...... 35
3.6.2 On-Track Performance Comparison ...... 36
4 Conclusions and Recommendations ...... 37
4.1 Conclusions ...... 37
4.2 Recommendations ...... 37
References ...... 39
A Engine Instrumentation Information ...... 40
A.1 Encoder, Mount, and Adaptor Shaft Drawings ...... 40
A.2 Kulite Pressure Transducer Drawings ...... 43
B Yamaha Genesis 80 Information ...... 45
C Additional Torque Usage Information ...... 47
D Matlab Code to Convert ACAP Files to Excel Files ...... 48
E Cylinder Pressure Traces and Comparison ...... 50
Page 4 of 57 Abstract
A competitive vehicle in Formula SAE needs to be easy for unskilled drivers to extract the maximum performance from. This requires a predictable and manageable torque curve. This report details the development of an intake manifold for a Formula SAE car from a vehicle-based approach to produce this manageable and predictable torque. The current vehicle was instrumented and driven on a representative track to determine the usage of available torque. Based on these findings an ideal torque curve was chosen that favored increased torque at upper engine speed ranges and decreased torque at lower engine speed ranges.
A 1-D engine cycle simulation model was developed and calibrated from intake, cylinder, and exhaust pressures measured on a dynamometer. The combustion model used the Wiebe function to model the burn rate and determine the simulated cylinder pressure. A design of experiments was performed with the calibrated 1-D model to find the optimized intake manifold geometry. Primary runner length and inlet diameter as well plenum volume were investigated and sized to produce as close to the ideal torque curve as possible. Based on this geometry a 3-D CAD model was developed and 3-D printed for use on the engine.
The fuel delivery and ignition timing of the engine with the 3-D printed intake manifold were tuned on a dynamometer and the torque curve produced was found to be similar to the predicted torque curve at the upper engine speed range but deviate at the mid-range. An on-track vehicle comparison of the new intake manifold to the old intake manifold was attempted but not completed due to cracking of the new intake manifold under vacuum on the vehicle.
Page 5 of 57 Chapter 1
Introduction
1.1 Background
1.1.1 FSAE Competition
In the Formula SAE (FSAE) collegiate design competition, engineering students from across the globe design and build open-wheel race cars to compete against each other. The drivers for MTU’s FSAE team are members of the team, and engineering students, not professional race drivers. For this reason, it is important to have an easy to drive and predictable vehicle. The torque delivery of the vehicle needs to be manageable and predictable for the driver to consistently drive at the limit. While a predictable and controllable vehicle is important, it is also important to have enough power for the vehicle to perform competitively. This means the torque curve is crucial to the overall performance of both the driver and vehicle.
The FSAE rules put many limitations on the engine, including:
Four Stroke, Reciprocating Piston Type Maximum Displacement of 710 cc All Intake Air Must Pass Through a Circular 20 mm Diameter Restrictor Throttle Body Must Be Before the Restrictor
Due to the limitations put on the vehicle by the rules, the budget limitations of the MTU FSAE team, and the limited high-performance driving experience of the drivers, it is important for the vehicle to be as optimized as possible.
Page 6 of 57
1.1.2 Intake Manifold Tuning
For a given engine displacement and technology, the amount of integrated torque, or “area under the curve” is largely fixed. The maximum torque generated at a given engine speeds is a product of the air and fuel burned in the cylinder. In a spark-ignited (SI) engine, air leads and fuel follows, meaning the output is controlled by controlling the airflow into the engine. Increasing the maximum airflow at a given engine speed, with an appropriate increase in fuel delivered, will increase the torque output at that speed. The amount of airflow into the cylinder at a given engine speed can be maximized by tuning the intake manifold to have ideal Helmholtz resonance characteristics [1]. This tuning is only ideal for certain engine speeds, and can negatively affect airflow at other engine speeds. Heywood [2] shows the effects of intake runner length on the volumetric efficiency (VE) of an engine across its speed range, which can be seen in Figure 1.1.
Figure 1.1: Volumetric efficiency for different intake runner lengths [2].
In Figure 1.1 notice that the longer runners increased VE at lower engine speeds, but decreased VE at higher engine speeds, and the short runners had the opposite effect. Therefore, the torque curve can be tuned by careful selection of intake manifold geometry.
Torque can be increased without sacrifice by adding “technology” such as forced induction, variable valve timing, active intake manifolds, etc., but at the cost of increased mass and cost. So
Page 7 of 57 to improve the performance of a FSAE race car without adding mass and cost, the torque needs to be generated efficiently, without wasting torque at engine speeds where it will be unusable due to wheel spin.
1.2 Hypothesis
Tuning the intake manifold geometry so the engine delivers an optimized amount of torque throughout the engine speed range will improve the overall vehicle performance in the form of lower lap times. Tuning the torque curve with the intake manifold so there is no “wasted” or unusable torque will mean the engine is working at its maximum effectiveness for the vehicle. The optimized torque curve will improve drivability because the vehicle will be less likely to break traction under power. Improving drivability can result in more consistent lap times with less driver fatigue, and more driver confidence. The improved confidence allows the driver to push the vehicle to the limit, extracting the maximum possible performance.
Page 8 of 57 Chapter 2
Procedure
2.1 On-Track Torque Usage Investigation
To optimize the intake manifold geometry for the lowest lap times, the target torque curve first had to be determined. This was accomplished by first determining how the torque previously available (old intake design) was used by the vehicle. With fixed atmospheric conditions, the torque an engine produces at any time depends only on the manifold absolute pressure (MAP) and engine speed, assuming consistent fueling. For example, running the same engine, with the same intake, exhaust, and fuel/spark calibration, on a dynamometer versus in a vehicle. So the torque the engine develops on-track can be determined by recording the MAP and engine speed then recording the torque on an engine dynamometer at the same MAP and engine speed points.
Since the FSAE competition only takes place once a year in May, the actual endurance track could not be driven so an accurate representation had to be developed to fit in the space available. A track was designed based on the FSAE track, featuring approximately 1/3 of the features, but with straights and a slalom the same length as the FSAE track. The overall track length was 1625’ (0.3 miles). Figure 2.1 shows the 2015 FSAE endurance track. Figure 2.2 shows the test track developed for the Houghton County Memorial Airport (CMX).
Figure 2.1: 2015 FSAE endurance track [3].
Page 9 of 57
Figure 2.2: CMX test track based on 2015 FSAE endurance track.
The engine parameters (engine speed and MAP) were measured using a Performance Electronics (PE) ECU, which has built-in data acquisition (DAQ) capabilities. Vehicle position and engine speed were measured using an AIM EVO4 DAQ system with built-in GPS. This data was aligned based on engine speed so it would be possible to determine engine torque and power on the track, such as mid-corner, corner exit, and on straights.
The test vehicle, the F194, was a race-proven chassis, having competed in the 2015 FSAE competition with the Yamaha Genesis 80 two cylinder engine. No aspects of the chassis or drivetrain were changed during the test. To gain a broader understanding of the torque needs, multiple intake manifold/calibration combinations were developed, with the goal being to have several power levels for the vehicle. This included a 19 mm intake restrictor, 25 mm intake restrictor, and appropriate engine calibrations. Table 2.1 below provides a breakdown of the intake/calibration setups used.
Table 2.1: Intake restrictor/calibration setups used during F194 track testing. Run Number Intake Restrictor Calibration 1 25mm 19mm Race Cal 2 25mm 25mm Cal 3 19mm 19mm Race Cal
Each combination was run for 3-5 laps around the test track, with the driver focused on being as fast as possible while still remaining consistent. To determine the torque and power used on track, the engine was run on the dynamometer at the same MAP and engine speed points. To accurately represent the vehicle, the exhaust system from the F194 was used on the dyno, with slight
Page 10 of 57 modification so the exhaust could be routed to the building exhaust vents. The header was unmodified so the primary exhaust runners were the same as the vehicle. The only thing different from the test track driving was the atmospheric conditions, which though recorded at the test track, were not recorded in the dyno cell during testing. The track testing temperature was 17 °C, while the dyno cell was thermostatically controlled around room temperature, approximately 21 °C.
The engine was run with the setups seen above from 4,000 rpm to 12,500 rpm while sweeping the MAP (opening and closing the throttle) at 500 rpm increments. PE was once again used to record MAP and engine speed, including the exact same MAP sensors used on-track. Dynomax software was used to record engine speed and torque, and the engine speed data was used to align the two sets of data. The post processing and results are discussed in Chapter 3.1.
2.2 Engine Model Development
Once the target torque curve had been established, a reliable model of the engine was needed to find the intake design that would best meet the torque target. This was achieved by developing a 1-D engine simulation using GT-Power, and was calibrated based on intake, cylinder, and exhaust pressures measured on a dynamometer. To measure these pressures, the engine was instrumented with several special pressure transducers and a crankshaft encoder recorded with a combustion analysis system. The data was recorded and reviewed, then input into GT-Power and the combustion model was calibrated.
2.2.1 Engine Dynamometer Testing
2.2.1.1 Engine Instrumentation
To obtain high-speed intake, cylinder, and pressure measurements, an ACAP combustion analysis data acquisition system, made by DSP Technologies, was used. Table 2.2 summarizes the ACAP hardware.
Page 11 of 57
Table 2.2: ACAP data acquisition hardware summary. Model Description DSP Technologies Porta 416 12 Slot Chassis 4325 TRAQ Real Time Processor 5008 8192K Memory Module 4012A TRAQ I System Controller 2860 4 Channel Timer/Digitizer 2904A Spincoder Timer/Counter 1104CM 4 Channel Charge Amplifier 6001 CAMAC Microprocessor
The ACAP combustion analysis system required a high-speed encoder reading engine position. A 720 pulse per revolution encoder was selected so pressure measurements could be made at every ½ degree of crankshaft rotation. An Encoder Products (EPC) Model 121 was chosen. It is a non- contact encoder that is compatible with the engine’s maximum angular velocity of 13,000 rpm. A data sheet on the EPC 121 can be found in Appendix A.
A mount was designed that pressed into a crankshaft bolt access hole on the ignition cover to rigidly mount the encoder on the engine. Figure 2.3 below shows the ignition cover of the engine that the mount was pressed into.
Figure 2.3: Yamaha Genesis 80 ignition cover, before the encoder mount was pressed in.
Page 12 of 57 A drawing for the encoder mount can be found in Appendix A. The encoder attached to the crankshaft via an adapter shaft designed to replace the flywheel bolt. A drawing of the encoder adaptor shaft can be found in Appendix A. Figure 2.4 shows the mount and shaft on the engine, with the encoder mounted.
Mount
Adaptor Shaft
Figure 2.4: Engine with EPC 121 encoder mounted. Note the aluminum encoder mount and steel adaptor shaft.
Initially the adaptor shaft was machined with a 15 mm OD, and the encoder was specified with an ID of 15 mm. This clearance proved too tight and the force required to press the encoder onto the shaft resulted in a cracked encoder rotor which led to complete encoder failure. The adaptor shaft was machined down so the encoder could easily slide on and a new encoder was installed.
The encoder signal was fed into the ACAP system with BNC cables for the A pulse (720 pulses/revolution) and Z pulse (1 pulse/revolution). ACAP uses the A pulse to trigger the recording of the intake, cylinder, and exhaust pressures.
The new encoder worked with the ACAP system at engine speeds below 6,000 rpm but an encoder error occurred at greater engine speeds. An attempted solution was to use a thin rubber sheet as an isolator for the encoder body, but this allowed too much movement between the encoder body and rotor, which resulted in encoder failure. The final solution was to mount the encoder directly to
Page 13 of 57 the mount, and retighten the mounting bolts and clamping bolt after every data collection run. There were no encoder errors below 11,500 rpm after this. Above this engine speed high-speed pressure data was not collected due to the encoder errors.
To measure pressure in the intake port a Kulite ETL-179X-190M piezoresistive pressure transducer was used. The cylinder head was machined to place the intake pressure transducer at the beginning of the intake port. The exhaust pressure was measured 25 mm after the exhaust port by welding a bung onto the header. This bung was drilled and tapped to accept the Kulite EWCTV- 312M pressure transducer. A drawing of the Kulite ETL-179X-190M and EWCTV-312M can be found in Appendix A. The Kulite EWCTV-312M is a liquid-cooled transducer. A 20 gallon/hour garden water fountain pump was used to pump tap water from a half-full five gallon bucket through the sensor and back.
The cylinder was machined for a PCB 115A04 cylinder pressure transducer. Due to the tight packaging of the head, only cylinder 2 was instrumented. Figure 2.5 shows the instrumented engine with the intake, exhaust, and cylinder pressure transducers in place.
Exhaust Pressure Transducer Intake Pressure Transducer
Cylinder Pressure Transducer
Figure 2.5: Instrumented Yamaha Genesis 80 cylinder head.
The signals from the three pressure transducers were fed into the ACAP system for high-speed acquisition. The high-speed pressure data was recorded for 300 cycles at each speed/load point. Table 2.3 provides a summary of the high-speed instrumentation.
Page 14 of 57 Table 2.3: High-speed instrumentation summary. Parameter Device Specifications Cylinder Pressure PCB 115A04 Pressure Transducer Sensitivity: 211.7 pC/MPa Intake Port Kulite ETL‐179X‐190M Pressure Range: 0‐2 bar absolute Pressure Transducer Exhaust Port Kulite EWCTV‐312M Pressure Range: 0‐3.5 bar absolute Pressure Transducer Engine Crankshaft Encoder Product Model 121 Resolution: 0.5 CAD Position
Other parameters of engine performance were monitored and recorded using L&S, such as torque, engine coolant temperature, engine oil temperature, intake air temperature, exhaust gas temperature (EGT), air/fuel ratio (AFR), engine speed, and fuel flow at 1 Hz. The low-speed data was collected at each speed/load point for the duration of the 300 cycles. Table 2.4 below provides a summary of the low-speed instrumentation.
Table 2.4: Low-speed instrumentation summary. Parameter Device Torque Land & Sea DYNOmite Dynamometer Strain Gauge Engine Coolant Temperature Type K Thermocouple Engine Oil Temperature Type K Thermocouple Intake Air Temperature Type K Thermocouple Exhaust Gas Temperature Type K Thermocouple Air/Fuel Ratio Innovate LC‐1 Narrowband Oxygen Sensor Engine Speed Land & Sea Hall Effect Sensor Fuel Flow Re‐Sol RS822‐85 Fuel Flow Measurement System
These parameters along with the pressure data would be used to calibrate the combustion model in the GT-Power simulation, which is discussed in Chapter 3.2.
2.2.1.2 Dynamometer Setup/Testing
The engine was loaded using L&S DYNOmite 9” Toroid water brake. This water brake uses a strain gauge to measure torque. The strain gauge torque measurement was calibrated at 0 ft-lb and 25 ft-lb using an L&S calibrated weight. Figure 2.6 shows the engine on the bedplate with the water brake attached.
Page 15 of 57
Figure 2.6: Engine setup on the test bed with the dynamometer attached.
The engine speed was electronically controlled using an L&S servo load valve, which regulates the amount of water going to the water brake using a PID controller to maintain a user-set engine speed. The throttle was electronically controlled using an L&S throttle servo. Data was collected with the engine at wide open throttle from 5,000 rpm to 11,500 rpm in 500 rpm increments.
2.2.2 GT-Power Model
The GT-Power model was developed based on an existing model the FSAE team had previously used. The model initially included accurate measurements of the cylinder geometry, camshaft profiles, camshaft centerlines, and cylinder head flow coefficients. These parameters can be found in Appendix B. The Gamma Technologies software GEM3D was used to accurately model the F194 intake manifold by importing a 3-D CAD file and converting it into flow components in GT- Power. Figure 2.7 shows the F194 model which was used to calibrate the combustion model based on the empirical data.
Page 16 of 57 Figure 2.7: Initial GT-Power model of the F194 used to calibrate the combustion function
Initially a turbulent combustion model was attempted, but due to the lack of reliable and accurate information for many of the required model inputs regarding the engine and cylinder head, the Wiebe function was chosen. Some of the additional pieces of information included detailed piston combustion chamber, and port geometry, intake port tumble measurements, and flame speed. The Wiebe function, which generates an “S” curve that represents the burning of the air/fuel mixture, can be seen in Equation 2.1 below [4].